Oriented films formed from polypropylene-based resin materials are used as various package films. For example, uniaxially oriented polypropylene-based films have a property that they are likely to be torn along the film-flowing direction during the film production, i.e., the longitudinal direction called machine direction (MD direction), and thus they are easily cut straight along that direction (straight cuttability). Therefore, they are widely used mainly in the field of food packaging.
While uniaxially oriented films comprising polypropylene-based resin materials are excellent in the straight cuttability along the MD direction, however, they are poor in the strength along the direction perpendicular to the MD direction (TD direction), and therefore they may be broken when used for packaging heavy contents.
As a film for packaging heavy contents having straight cuttability and improved strength along the TD direction, there have been known those produced by a method utilizing polypropylene formulated with polybutene (Japanese Patent Unexamined Publication No. 7-156264). While this method improves the strength along the TD direction, however, it cannot afford straight cuttability along the MD direction at a sufficient level. In addition, it suffers a problem concerning the cost, because it utilizes a large amount of expensive polybutene.